Growing and Dividing Perennials and Shrubs

Propagation - growing and dividing perennials and shrubs

Paula, Mill Pond Flower Farm

Choosing Perennials for your patch

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Perennials and shrubs can be the backbone of your cut flower enterprise. When well established they can be a relatively low maintenance crop, providing good quantities of stems across the whole season. They can give colour, shape, height and texture. The huge variety of perennials and shrubs can give you scope as a grower to develop your own style and identity by choosing particular varieties to grow as cut flowers.

Some growers might choose to specialise in a particular plants, growing larger quantities to supply to florists or wholesalers of flowers such as peonies, delphiniums, physocarpus or astrantia. 

What to consider when choosing your perennials and shrubs:

  • Will it cut well? (More on this in Module 9)

  • Do I have a market for the flower or foliage? (Much more on this in Module 2)

  • What Soil Type does it like?

  • What Soil pH does it need?

  • Right plant, right place – where does it need to grow?

Some perennials will be better grown as annuals by cut flower growers, depending on the soil type and climate. For example, Claire grows achillea as an annual in Surrey, as it’s not so productive in year 2 on her chalky soil. However, in Scotland on heavy clay it takes a year to actually get going so is a short-lived perennial. I usually get two years before it needs replacing by seed grown plants or cuttings. Anthemis tinctoria is only properly productive for a year though, so I tend to grow new plants from seed every year, or collect self-seeded plants in the winter.

Perennial propagation

Sowing seeds

Most perennials can be grown well from seed.  The best time to sow is when the plants naturally set seed – for spring flowering perennials that’s usually in the summer, summer flowering in the autumn and autumn flowering in spring. A lot of seed companies give very general advice on perennial seed sowing, so it’s worth doing a bit of research to find out if there are any particular requirements for the seed you’re sowing. 

Many perennials for cooler climates need a period of vernalisation or cold, and just won’t germinate without it. Others don’t respond well to the general advice for seed sowing. 

I followed the instructions for sowing achillea for years (plant in spring, in warmth 18-20 C) with very little success until Claire told me to ignore the packet as they like to grow in cool conditions. Now I have full trays of achillea! 

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Division

Most gardening books recommend dividing perennials, which is fine if you’re dividing them because they’ve got too big. The year after division usually results in fewer flowers however, as the plant has been significantly disturbed, so it’s worth bearing that in mind when you’re growing for cutting. 

General advice is to divide Spring/early summer flowering perennials in the autumn and late summer/autumn flowering perennials in the Spring. However, time constraints in the spring mean that I usually move or divide perennials in the winter, starting with the earliest flowerers and moving through to the later ones. 

Taking cuttings

Lots more plants for free! Many perennials can be propagated by cuttings and this leaves the main plant undisturbed. It’s also a great way to create more of a particularly good specimen as the offspring are clones of the main plant. 

Claire taking cuttings.jpg

Our Top tips for productive perennials for your soil type

Late May bouquet, with mostly perennials, - Delphinium, Centaurea, Geum and Dicentra (plus ranunculus, bluebells and mint)

Late May bouquet, with mostly perennials, - Delphinium, Centaurea, Geum and Dicentra (plus ranunculus, bluebells and mint)

Perennials are great for 

  • Times of the season when annuals are just getting started or just finishing - e.g May/ June and October

  • Keeping flowers going in hot dry periods and wet cold periods

  • Having a 2nd flush

  • Don't go over quite as quickly, so better if you don't pick every day

  • Reliablity, in permanent plantings.

  • Lower on maintenance, although will need splitting occasionally

  • Often less common in wholesalers so florists are keen on using them

Our best growers

Clay soil type - Paula in Scotland

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 Lupins : Grown from seed,  mine are all Russell Hybrids. Very easy to propagate each year from seed, and reliable. We start to cut in late May, and they go on until July, then usually a 2nd flush September/ October. If you sow seeds in the spring, they usually flower August to September in their first year.

Astilbe : My best variety came from a landscaper (gift) - others have been bought as plants from local wholesalers Mac plants,  so they are recommend for this area. They flower July to August and they do well in damp soil. Very popular with florists and if there are any left, they dry really well.

Delphiniums : All grown from seed, - most are Belladonna varieties. Shades of blue are stronger than the white plants (which are the florist's favourite) They flower June to August and then a 2nd flush late August to September (smaller flowers) - The first batch can be huge flowers, so hard to transport. 

Hellebores : Stars of the early season, these grow well in heavy soil. Need a quick weed in early Autumn, but then get on with growing and flowering. They bulk up quite quickly so they can be split in Autumn, or Spring. 

Echinops: Grown from seed, these are hard to get rid of if moved, as they can be multiplied by root cuttings, so we've now got 2 clumps. Very reliable in blue and white. Prolific, easy to grow and dries well. 

Chalk soil type - Claire in Surrey

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Phlox: My best variety is a pink one that has been multiplied many times from a garden plant. Easy from divisions, scented, and ball headed in July before the Dahlias start, this is an amazing flower for me to grow a full 10 metre bed of plants. (I’ve actually got 40 m planned for next year in many colours!)

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Centaurea : This blue and white perennial cornflower starts in late April, and flowers all through May. It then has a 2nd flush in September/ October at a time when blue is a scarce colour. With 5- 10 stems coming from each plant each week, it's not as prolific as the annual forms, but is easy to look after.

Geum : The bright oranges and reds of Geums are a wonderful late spring colour burst. Their only problem for me is that they are a deer's favourite snack - Protect!

Leucanthemums : Daisies were never my favourite flowers in gardens, but i've found that they are a total favourite in brides DIY buckets, and they last in the vase so much longer than they look like they should. Easy to divide and multiply, i've got both single and double varieties, and they give me 4 weeks of colourful flowers

Hellebores: I wouldn't want to start my season without Hellebores. Both at home and the farm i can enjoy the flowers myself for a few weeks in early spring, and then sell the flower heads when they start to go to seed. A couple of quick 10 minute weed sessions a year, and a bit of leaf mould are all they need to keep them wonderfully productive.

Sandy soil type - Carol in Cheshire

Achillea from seed, also easy to grow from division

Achillea from seed, also easy to grow from division

Achillea: Very long season from Mid July to October in a wide range of colours, very reliable. Easy to grow from seed and division. Very drought tolerant, and needs staking here.

Astrantia: Has to have the very best conditions we can offer here - the dampest and with a bit of shade at the hottest part of the day. But, we get a long season of flowers - from June to October, if we keep cutting all the flowers. You can grow it from seed, but it goes into dormancy, so it needs to be very fresh seed, or exposed to cold over winter, or sometimes both! Or you can divide it, but we’ve found that it can sulk if you divide in winter, better when it is growing well eg late spring.

Nepeta: I grow Six Hills Giant. It loves the conditions here, and thrives even in last year’s drought, on sandy soil in full sun, with zero watering. It flowers June-July and again in Sept to Oct if you cut it all back after the first flush. Very easy to propagate from divisions or cuttings.

Marjoram: I grow several marjorams and oreganos. My favourite is an ordinary marjoram which has a dainty white flower. It is good in bouquets and out of water (strip leaves off first), so it’s a great gyp replacement. Propagate from seed, division or cuttings. We have a patch in the tunnel which grows 70cm tall and flowers late July, outside it grows 40-50 cm and flowers Aug- Sept. and it’s scented!

Mint: Absolutely everyone seems to love mint. We grow lots of varieties, to have different leaf colours and different flower colours, different periods of flower. They all need a moist soil and some shade here. We sell and use masses. Cut down any unused flower stems after they’ve gone over and you get a second flush of green stems to use for foliage. With a good mix of varieties, you can be cutting continuously from May to October. My favourite for scent is applemint, but that does suffer from mildew in dry spells.

Shrubs - Planting and moving

Planting Shrubs

Autumn can be the best time for planting or moving shrubs. They can often be bought bare root, and the cool temperatures will give them time to get established with plenty of moisture in the soil. 

If you’re buying plants, for best results look for locally grown from at least as far north as you are based. It’s a lot to expect from a shrub to adapt to a much colder climate.

Once planted and watered in, try to mulch well. A good mulching will provide the roots with steady moisture and an insulating layer from the worst of the ice and snow. It’s amazing the difference a few inches can make to the temperature – on a frosty morning, try taking the temperature of the ground and then 4 or 5 inches below soil level. The soil temperature is well maintained even on the coldest of days and that’s where the roots of your shrubs are resting. Mulches keep the temperature even, weeds at bay, and are also a great moisture retentive barrier for the summer. The difference between mulched and bare soil this year was striking and, although we can’t guarantee heatwaves every year, the unpredictability of the weather makes mulches a long term buffer against extremes. 

Top 5 in Clay-  Paula in the Scottish borders

Birch

Planted as whips about 15 years ago, we're fortunate to have a good supply of birch. The trees grow quickly and we're in the process of coppicing them to allow more cutting. Birch is my top seller of all flowers and foliage - it's good out of water and is sold for wreath bases in the run up to Christmas. A long term option for shrubs but a very good one. Once it's growing it requires no attention but does like moist ground.

Escallonia

I've bought a white flowering variety (Iveyi) and also have bushes grown from donated cuttings that flower red and pink. It grows quickly and well, forming arching stems of dark green glossy leaves. Once planted and if cut regularly for foliage it needs no real care. 

Jasmine

I've had one plant growing in the corner of a polytunnel for the past 7 years and cut hundreds of stems from it every season. I've added a wall of new plants growing up wires to increase availability. Fed a couple of times a year and cut regularly and hard as soon as it's in leaf, a star performer and really popular with florists. 

Eucalyptus

Mostly grown from seed, a couple of plants bought in and a few purloined from Carol Siddorn's Cheshire plot. They all do well and I've cut a few hundred stems from them in the past few weeks. Most are gunnii or parvifolia but I've also grown dalrympleana from seed this season and it's doing well. They don't seem to mind the cold and wet and are providing a good hedge to protect other shrubs.

Ligustrum

We had some very old Ligustrum (privet) that I tried to dig out but couldn't get rid of it. It's now one of our most useful and profitable shrubs! It's tough as old boots, semi-evergreen so can be used early in the season, good out of water, and increasing in popularity for florist orders. It needs absolutely no care.

Top 5 Sand - Carol in Cheshire

Eucalyptus : It somehow seems a bit of a foliage cliche now, and it’s so widely available - but you really can’t beat the scent and character of freshly cut eucalyptus. I’ve always loved it and will always have some if I can. We have lots of E parvifolia and E gunnii which are reliably hardy here (survived -10.5C here last winter), as well as some other more interesting species. I’ve grown all of them from seed, they don’t easily take from cuttings if at all.   I cut it from Sept to end April, most of them back to a pollarded stem, and then let it regrow for the summer. I have some on a different cutting regime to get stems that I can use during summer and autumn before the main crop is ready. Less efficient, but gives me stems out of the normal season. In the photo, you can see pollarded ones in the foreground, un-pollarded behind. If we start cutting too early in the year it will be too soft and may wilt - and you loose the extra growth potential compared to leaving it til late summer/early autumn

Physocarpus : we grow three varieties of this and it’s the strongest colours we have in summer. It’s brilliant with dahlias for hot schemes as well as more muted palettes. There are loads of new varieties available now. Previous year’s wood will flower in late spring, followed by good, textural coloured seed pods. It needs good conditioning as it can wilt if cut too soft.

Spirea : we have 6 varieties of Spirea, but the best are any of the white ‘Bridal Wreath’ ones which flower in spring. If you plant different types, in different locations, you can get a good succession of flowers from early May to mid June. Most of them drop petals, sadly, but as it’s white, it looks quite pretty.

Abelia grandiflora : this is probably my favourite shrub. It is hardy here, but is occasionally damaged by cold winds winter - though all plants have survived to -10C. It’s main season is Sept - Oct and later, when it has lovely coral bracts and pale pink flowers. I sometimes pick off the pink flowers and just use the bracts, which last well out of water.

Rosemary : This has always been hardy here, but we did lose a couple in a cold windy winter. I mainly grow Miss Jessop’s Upright as it has good long stems, but I also have an ordinary culinary one for buttonholes etc. We have had Rosemary beetle for the last couple of years, but I don’t yet know how bad it’s impact will be. This is the single foliage I am most often asked for.

Top 5 Chalk - Claire in Surrey

Senecio: Officially called Brachyglottis, but I hate that name. I was given some donated cuttings from a Garden society plant sale when I first arrived at the farm. In year 3, 2 plants (cost, nothing) gave me a total of 130 stems. So I've added 80 more plants.  I don't like the flowers, but then I cut it so hard, it never gets a chance to flower on my field. My florists love it for bridal bouquets, and you can pick it almost all year round. (Although if the deer have a nibble in spring, it's fine again by July)

Physocarpus : The nine bark took a couple of years to get established on my chalk, but now it provides a wonderful colour foliage, and although I'm sure it isn't as vigorous as on chalk or in Carol's sand, it does well enough to merit a decent area of our shrub bed.

Rosemary : I sell hundreds and hundreds of stems of this to florists, and I use it regularly in farewell flowers and in my own bouquets. Wonderfully scented, it is great for straight stems, and it seems that the harder you cut it the better it comes back. I also have rosemary beetle. Regular picking off by the teen (teenage son) is my method of defense.

Hypericum : When I was planning my flower farm, I visited Arjen Heuse who was flower farming at that time in Sussex. He introduced me to the berried Hypericum and I've loved it ever since. I bought 5 PBR varieties, but I have 6!, Salmon, Peach, Red, Green, Black and Cream. Florists love them all, and they are a great late summer addition to DIY buckets.

 Viburnum: My favourite Viburnum is Tinus, which provides me with flowers and seed heads for the first bouquets of the year, and glossy green foliage for late Autumn. I'm sure if it was growing with Paula it would be 7 ft tall, but I've found that 30-40cm stems are brilliant and can last 3-4 weeks in a bouquet.